In a multicarrier mobile communication system, a Base Station (BS) performs downlink data transmission to User Equipments (UEs) in one or more cells. The BS needs to allocate communication resources in the time-frequency domain to each UE when the BS transmits downlink data to a specific UE since a plurality of UEs may be present in a cell and each UE does not know when and in which format data will be transmitted to the UE. The BS transmits information of such resource allocation to each UE by transmitting a control signal including the resource allocation information to the UE.
In order for each UE to transmit data packet in the uplink, the BS also needs to allocate communication resources in the time-frequency domain to each UE and to transmit control information to allow the UE to transmit data through the uplink.
When the BS allocates resources for data transmission in the uplink/downlink, for example in the OFDM system, the BS can define a small unit such as one subcarrier, a large unit such as tens of subcarriers, or a larger unit as a basic unit of the allocation.
When small allocation units such as subcarriers are used for resource allocation of the BS, resource allocation information for data transmission, which the BS transmits to each UE using a control signal, includes all information as to whether or not each subcarrier is allocated to the UE, thereby increasing the overhead. On the other hand, when larger allocation units are used, there is an advantage in that the overhead is reduced while there is a problem in that the flexibility of resource allocation is reduced since each UE cannot be allocated small resources for data transmission.
For example, let us assume that 576 subcarriers can be used for downlink data transmission in an OFDMA system with subcarrier intervals of 15 KHz in a 10 MHz system band. In this case, if a single basic resource block as a minimum unit of resource allocation is designed to include a unit time of 0.5 ms and 12 subcarriers, the total band is divided into 96 basic resource blocks every 1 ms and, when transmitting data to each UE every 1 ms, the BS must inform the UE of which one of the 96 basic resource blocks is used to transmit the data to the UE through resource allocation information such as scheduling information.
Here, in order to allow a scheduler of the BS to transmit data through any basic resource blocks to any UE under no constraints, a scheduling command for each UE must include 96-bit information individually representing the used resource blocks. Specifically, if signaling for resource allocation informs each UE whether or not a corresponding resource block has been used according to whether a specific bit is “0” or “1”, the signaling for resource allocation will require 96 bits, resulting in large overhead.
However, using a larger number of subcarriers as a base resource block unit to reduce the overhead causes problems in the flexibility of resource allocation. For example, if transmission data, which has an amount to be transmitted through 36 subcarriers for 1 ms, is generated in a transmission buffer for a UE when 72 subcarriers are set as a base resource block unit, the BS must transmit the data using a larger amount of frequency-time resources than required since a basic resource block consists of 72 subcarriers or must delay the transmission until another data to fill the basic resource block is generated for the UE.
Accordingly, there is a need to provide a resource allocation method, which can overcome these resource allocation flexibility problems and the above resource allocation information overhead problems, and a method for transmitting resource allocation information for the same.